I have two table and like to know how many downloads a certain name has. Here are my tables
Table "names"
ID | name
==========
1 | foo
2 | bar
3 | zoo
4 | luu
Table "downloads"
ID | name_id | timestamp
=========================
1 | 1 | 1394041682
2 | 4 | 1394041356
3 | 1 | 1394041573
4 | 3 | 1394041981
5 | 1 | 1394041683
Result should be:
ID | name | downloads
=====================
1 | foo | 3
2 | bar | 0
3 | zoo | 1
4 | luu | 1
This should be pretty easy...
It is pretty easy.
Just JOIN tables and COUNT rows. Don't forget to GROUP BY, and COUNT(timestamp) so you could get zero if there isn't any
SELECT n.ID,
n.name,
COUNT(timestamp) as downloads
FROM names n
LEFT JOIN downloads d
ON d.name_id = n.id
GROUP BY n.ID,
n.name
ORDER BY n.ID;
SQL Fiddle
Related
I have a MySQL table like so:
id | day | item
---------------
1 | 1 | A
1 | 2 | B
1 | 3 | A
2 | 1 | C
2 | 2 | C
2 | 5 | B
3 | 6 | A
3 | 7 | C
I want to get the last item per id by day. So the output would be something like:
id | day | item
---------------
1 | 3 | A
2 | 5 | B
3 | 7 | C
What is the best way to accomplish this?
I know how to do this when the last day is the same for all ids, but I don't know how to do it in the case when each id may have a different last day.
This should work:
select table.* from table
join (select id, max(day) as day from table group by id)
as m on m.id = table.id and m.day = table.day
I have the following query:
SELECT
items.*
FROM
`items`
INNER JOIN
`users` ON `items`.`owner` = `users`.`id`
GROUP BY
`items`.`owner`
LIMIT
10
I ensures it is grouped by the user (only one item fetched per user), but I also wish ensure that items with the category, say, "1" only appears once.
But that does not work. Well, query succeeds, but it does not group by category. Multiple categories is still shown. Any ideas?
I have created a SQLFiddle here: http://sqlfiddle.com/#!2/0a4bad/1
Instead of outputting:
+----+----------+-------+
| ID | CATEGORY | OWNER |
+----+----------+-------+
| 1 | 1 | 1 |
| 2 | 1 | 2 |
| 3 | 1 | 3 |
| 4 | 2 | 4 |
| 5 | 2 | 5 |
+----+----------+-------+
It should be outputting:
+----+----------+-------+
| ID | CATEGORY | OWNER |
+----+----------+-------+
| 1 | 1 | 1 |
| 4 | 2 | 2 |
| 5 | 2 | 4 |
| 5 | 2 | 5 |
| 8 | 3 | 3 |
+----+----------+-------+
(notice category 1 is only shown ONCE).
I want to ensure that only one item per owner is shown, and then adtionally ensure that a specific category (say 1 and 5) is only shown once. The category 1 and 5 are overpopulated, and if they are not limited, they will be 90% of the output.
You can use DISTINCT to retrieve unique data:
SELECT DISTINCT items.category
select * from items t1
where category not in (1,2)
or not exists (
select 1 from items t2
where t2.id < t1.id
and t2.category = t1.category
)
group by owner
http://sqlfiddle.com/#!2/0a4bad/27
I have four tables and like to know how many locations and downloads a certain name has.
names and locations are connected via the names_locations table
Here are my tables:
Table "names"
ID | name
=========
1 | foo
2 | bar
3 | zoo
4 | luu
Table "locations"
ID | location
=============
1 | Hamburg
2 | New York
3 | Singapore
4 | Tokio
Table "names_locations"
ID | location_id | name_id
==========================
1 | 1 | 1
2 | 1 | 2
3 | 2 | 2
4 | 3 | 3
5 | 1 | 2
Table "downloads"
ID | name_id | timestamp
=========================
1 | 1 | 1394041682
2 | 4 | 1394041356
3 | 1 | 1394041573
4 | 3 | 1394041981
5 | 1 | 1394041683
Result should be:
ID | name | locations | downloads
=================================
1 | foo | 1 | 3
2 | bar | 3 | 0
3 | zoo | 1 | 1
4 | luu | 0 | 1
Here's my attempt (without the downloads column):
SELECT names.*,
Count(names_locations.location_id) AS location
FROM names
LEFT JOIN names_locations
ON names.ID = names_locations.name_id
GROUP BY names.ID
I think this would work.
SELECT n.id,
n.name,
COUNT(DISTINCT l.id) AS locations,
COUNT(DISTINCT d.id) AS downloads
FROM names n LEFT JOIN names_location nl
ON n.id = nl.name_id
LEFT JOIN downloads dl
ON n.id = dl.name_id
LEFT JOIN locations l
ON l.id = nl.location_id
GROUP BY n.id, n.name
All of those seem to work. here's another one.
SELECT
a.ID,
a.name,
COUNT(c.location) AS locations,
COUNT(d.timestamp) AS downloads
FROM names AS a
LEFT JOIN names_locations AS b on a.ID=b.name_id
LEFT JOIN locations AS c ON b.location_id=c.ID
LEFT JOIN downloads AS d ON a.ID=d.name_id
GROUP BY a.name
SELECT
t.id,t.n AS name,
count(location_id) AS locations,
t.downloads
FROM names_location
RIGHT JOIN
(SELECT
names.id AS id,
names.name AS n,
count(timestamp) AS downloads
FROM names
LEFT JOIN downloads ON names.id = downloads.name_id
GROUP BY id) AS t
ON t.id = names_location.name_id
GROUP BY t.id
Output:
+------+------+-----------+-----------+
| id | name | locations | downloads |
+------+------+-----------+-----------+
| 1 | foo | 1 | 3 |
| 2 | bar | 3 | 0 |
| 3 | zoo | 1 | 1 |
| 4 | luu | 0 | 1 |
+------+------+-----------+-----------+
4 rows in set (0.00 sec)
I have the following table structure:
item_id | value |
==================
1 | 1 |
1 | 3 |
1 | 4 |
2 | 2 |
2 | 3 |
2 | 4 |
2 | 5 |
3 | 1 |
3 | 5 |
3 | 6 |
4 | 1 |
4 | 3 |
4 | 4 |
4 | 5 |
I have a query that returns those item_id whose value matches with 1, 3 and 4.
So here, the item_ids that should be returned are 1 and 4.
My query:
select item_id from table t
where exists (select item_id from table t1 where value = 1 and t1.item_id = t.item_id)
and exists (select item_id from table t1 where value = 2 and t1.item_id = t.item_id) group by item_id
This query is working fine. Here i am matching only 3 values. What if i want to match 50 such values from the table? (all the 50 values are stored in a php array) The query will be huge and also i want to do the same thing from two different tables in the same query. So, this will double the size of an already huge query. Please suggest me some other way around.
Edited::
table 2
--------
item_id | user_id |
==================
1 | 1 |
1 | 5 |
1 | 7 |
2 | 2 |
2 | 3 |
2 | 4 |
2 | 5 |
3 | 1 |
3 | 5 |
3 | 6 |
4 | 1 |
4 | 3 |
4 | 4 |
4 | 5 |
Now, i want item_id where values from table1 are 1,3,4 and user_id from table2 are 1,5,7
This problem is called Relational Division.
SELECT item_ID
FROM tableName
WHERE value IN (1,3,4)
GROUP BY item_ID
HAVING COUNT(*) = 3
if uniqueness was not enforce on column value for every item_id, DISTINCT is required to count only unique values,
SELECT item_ID
FROM tableName
WHERE value IN (1,3,4)
GROUP BY item_ID
HAVING COUNT(DISTINCT value) = 3
SQLFiddle Demo (both query included)
SQL of Relational Division
I've got two tables in my database. Table 1 is a list of "timelines" and their corresponding owners and title.
Table 2 is a list of users who have access to the timelines but are followers, not owners.
I'm trying to write a query that outputs the lineID's and corresponding titles that are linked to a userID in either of the two tables.
A query for userID 1 would ideally output:
1 a
2 b
3 c
6 f
Hopefully this isn't too confusing but the purpose is to fill a dynamically generated select box with the LineID and Title for a given UserID...
Table 1 ("owners")
--------------------------
| LineID | UserID | Title |
| 1 | 1 | a |
| 2 | 1 | b |
| 3 | 1 | c |
| 4 | 2 | d |
| 5 | 2 | e |
| 6 | 1 | f |
--------------------------
Table 2 ("followers")
----------------------------
| RowID | LineID | UserID |
| 1 | 1 | 1 |
| 2 | 1 | 2 |
| 3 | 3 | 1 |
| 4 | 3 | 2 |
| 5 | 2 | 2 |
| 6 | 6 | 1 |
----------------------------
I tried using:
SELECT title
FROM `lines`
LEFT JOIN follow
ON follow.user_id = lines.user_id
WHERE follow.user_id = 1
That ended up producing duplicate rows.
The output I need would ideally be an array consisting of all the lineID's and Titles associated with that userID.
select LineId, Title
from owners
where LineId in (select LineId from followers group by LineId )
order by owners.LineId